Many vehicles include a drive-by-wire system that applies electronic sensors to relay driver input to an electronic control module (“ECM”). The ECM calculates driving of appropriate actuators to respond to the driver input. One subsystem commonly controlled by the ECM is an electronic throttle control system.
A vehicle's accelerator pedal is connected to the ECM by electronic circuits that transduce the accelerator pedal position into corresponding electrical voltages that the ECM applies to position the vehicle's throttle. When the driver is not applying any pressure to the accelerator pedal, the throttle will be at the idle position. When the driver applies sufficient pressure to the pedal to move it through its entire range of motion, the throttle will be at the wide open position. The rise and fall of the voltages in between the idle position and the wide open position reflect the pressure exerted by the driver on the accelerator pedal, which translates as a request for an increase or decrease in acceleration.
The accelerator pedal is a critical element for the safety and drivability of the vehicle. As a result, the ECM typically samples pedal voltages at a rate in the kHz range to monitor the condition of the accelerator pedal while it is being depressed or released. When the driver pushes on the throttle pedal, the corresponding voltages sent to the ECM by the throttle pedal circuits increase. In response to the increase in voltage, the ECM causes throttle position motors on cylinder heads in the vehicle's engine to move a butterfly valve to a position that will provide an increase in the air-fuel mixture provided to the cylinder, resulting in an increase in acceleration.
When the driver reduces the pressure on the throttle pedal, the corresponding voltages sent to the ECM by the accelerator pedal circuits decrease. In response to the decrease in voltage, the ECM causes the throttle position motors to move the butterfly valve to a position that will provide a decrease in the air-fuel mixture provided to the cylinder, resulting in an decrease in acceleration.